This invention relates to topically administrable ophthalmic formulations of brimonidine. The formulations of the present invention are solutions that contain 0.2% or less of brimonidine tartrate.
The topical use of brimonidine to lower intraocular pressure in patients with glaucoma or ocular hypertension is known. The first ophthalmic brimonidine product in the U.S. was approved by the FDA in 1996. That product, sold under the trade name Alphagan, contained brimonidine in the form of brimonidine tartrate at a concentration of 0.2%. The preservative contained in Alphagan is benzalkonium chloride, the most widely used preservative for topical ophthalmic compositions.
In 2001, a second ophthalmic brimonidine product was approved by the FDA. This product, sold under the trade name Alphagan P, contained brimonidine tartrate at a concentration of 0.15%. The preservative contained in Alphagan P is chlorine dioxide. See U.S. Pat. Nos. 5,424,078 and 6,562,873.
Chlorine dioxide is not an ideal preservative ingredient. It is an oxidative preservative. It is difficult to stabilize and is light-sensitive. Additional topical formulations of brimonidine are desired.